1. Field of the Invention
The invention relates to roller elements of a rotary printing machine and, more particularly, to a roller element for pressing a flexible priming plate against the form cylinder of a printing group of a rotary priming machine during a plate change.
2. Description of the Prior Art
Roller elements are well known in the art. For example, Japanese Patent Document No. 1-176558 discloses a device for mounting and removing a flexible printing plate. When the printing plate is wound onto or off the form cylinder, two rollers are used to press the printing plate against the rotating form cylinder. The rollers are separated from one another and each roller is placed into position by a working cylinder. The rollers are rotatably fastened to the piston rods of the working cylinder. This device is disadvantageous in that, during the removal of the printing plate, the rollers become smeared with ink from the inked image on the printing plate. Before a new printing plate is mounted, the rollers must be cleaned, which is a time-consuming process. If the rollers are not cleaned they will smear the new printing plate, resulting in smeared sheets at the start of the printing process and continuing until the printing plate becomes clean during the course of priming.
German Patent Document No. DE 42 18 602 C2 describes a pressing roller located on the form cylinder in a stationary manner. This device has the disadvantage that the pressing roller becomes contaminated by ink splatters and ink mist. In addition, a new printing plate is smeared with ink by the pressing roller when it is mounted.
It is thus desirable to provide a pressing roller which does not smear a printing plate with ink during mounting.